1. Field of the Invention
This invention relates generally to a wheeled vehicle designed to turn about a central vertical axis. In particular, the invention relates to circular powered utility omni-directional vehicles that are revolvably coupled to tow bars, material handling tools, vehicle chassis, or other appendages.
2. Description of the Prior Art
Within many industries, utility vehicles are often routed through crowded and busy terminals, warehouses, yards, or lots. Space is often at a premium, resulting in limited maneuvering space. Conventional vehicles are typically long, configured with two axles, one in front, the other in the rear. The rear axle is fixed to the frame of the vehicle and provides motive force via a pair of dual wheels. The front axle provides for vehicle steering via two steerable wheels which simultaneously pivot with a limited angular range.
Because there is a fixed distance between the fixed rear drive axle and the front steerable axle, a turning radius exists that far exceeds the space actually occupied by the vehicle itself. The longer the distance between front and rear axles, the larger the turning radius that is required to change directions of the vehicle. A large turning radius makes maneuvering around tight areas difficult and often dangerous. In an area where movement is constrained, a vehicle with a small turn radius is advantageous. Any increase in maneuvering efficiency and safety generally amounts to significant cost savings. It is desirable, therefore, to have a vehicle with greater maneuverability to enhance the safety of the operator, passengers, the surrounding environment, and nearby pedestrians.
Vehicles that have increased maneuverability are known in the art. For example, a circular omni-directional vehicle (ODV) is disclosed U.S. Pat. No. 6,581,703, issued to Hammonds (Jun. 24, 2003), illustrated herein as FIGS. 1-2. The ODV (208) includes two primary drive wheels (212L, 212R) mounted on a frame (214) which preferably has an outer perimeter in the shape of a circle. The circular frame preferably has a central vertical axis (216) which is perpendicular to the plane of the top view of FIG. 1. The wheels (212L, 212R) are mounted along a horizontal axis (218) which intersects the vertical axis (216) as shown in FIGS. 1-2.
A power source (222) mounted on the frame (214) is provided for driving the vehicle. The power source may be a battery, diesel or gasoline engine with generator, or other suitable source. The power source provides power to separate electric motors (226L, 226R), one for each wheel (212L, 212R). However, the power source may alternatively drive a hydraulic pump (not shown) which powers the individual hydraulic motors to turn the drive wheels. The speed and direction of rotation of the motors (226L, 226R) and wheels (212L, 212R) are controlled by the positioning of control levers (231L, 231R).
The control levers (231L, 231R) and motors (226L, 226R) operate exactly the same for each of the left and right wheels (212L, 212R), respectively. Each lever has a central neutral position, such that when a lever is at the neutral position, a wheel associated with that lever is preferably freewheeled or braked. If a lever (231L, 231R) is moved forward, the corresponding wheel motor (226L, 226R) rotates in a forward direction for turning a respective wheel (212L, 212R). If a lever is moved backward, the corresponding wheel motor rotates in a backward direction for turning a respective wheel. The greater distance that a lever is pushed or pulled from its neutral position, the faster the corresponding wheel motor turns, thereby causing the connected wheel to increase in speed.
If both levers (231L, 231R) are moved in the same direction and amount at the same time, both drive wheels (212L, 212R) move at the same speed, thereby causing straight-ahead movement of the ODV (208) over the ground, perpendicular to the horizontal axis (218). If the levers are pushed forward or backward at an unequal distance from each other, the lever moved the greater distance will produce a greater speed of rotation at its corresponding wheel causing the vehicle to turn toward the wheel that is turning slower. For example, if the right control lever (231R) is pushed farther forward than is the left lever (231L), the ODV (208) turns to the left, and vice versa.
If the right lever (231R) is moved forward and the left lever (231L) is moved backward and both lever positions are the same in amount and opposite in direction, the left wheel (212L) turns backward and the right wheel (212R) turns forward, both at the same rate of rotation. In this instance, the ODV (208) turns in its own space or footprint while its footprint remains stationary over ground, i.e., the ODV revolves about the vertical axis (216). (The ODV footprint is the area of the ground beneath the ODV's circular perimeter.) The counter-clockwise rotation described above becomes a clockwise rotation when the right wheel (212R) rotates backward at the same rate as the forward rotation of the left wheel (212L). Thus, the ODV (208) can change its heading while not moving or varying its footprint over the ground during such a change of heading.
The ODV (208) can move omni-directionally about a given point, change directions with zero maneuvering room beyond the physical footprint of the vehicle, and push or pull attachments with precise control. These capabilities reduce the operating space on the ground required to maneuver, thus increasing operating efficiency. Safety is increased because the operator of the vehicle, positioned in the operator's seat (250) directly at the center of the ODV, can always be facing the direction the vehicle is moving, never having to back up and look backward.
Referring to FIGS. 1 and 2, one or more swivel casters (213) support the ODV (208) and keep it from toppling. A circumferential rail (238) provides a bearing race for supporting a trolley hitch (224). The trolley hitch, which is used to attach a push bar (225), rolls or slides along the circumferential rail, but as the push bar forces are concentrated at the point if the rail where the trolley is located, the rolling or sliding motion may be hindered by the high localized forces and concomitant higher friction forces.
As shown in FIG. 3, the Hammonds omni-directional vehicle may also be used to tow a number of trailers. An omni-directional tractor (310) with drive wheels (312) and swivel casters (313) is removably coupled to a train of ODV trailers (311) using a trolley hitch (302) that freely slides along an outer circular rail (338) of the tractor. A hitch tongue (341) is fixed to each ODV trailer (311) perpendicular to and bisecting its trailer axle (360) for coupling to the trolley hitch (340) of the ODV in front of it. Each trailer also includes an outer circular rail (339) and partially revolvable trolley hitch (340) for towing an ODV trailer behind it. Each trailer has an axle (360) with two freewheeling wheels (362) and one or more swivel casters (313) for support.
FIGS. 4 and 5 illustrate a prior art ODV (510) equipped with a forklift tool (515), although other material handling tools are known in the art and may be used. Such ODVs are taught in U.S. Pat. No. 6,830,114, issued to Hammonds on Dec. 14, 2004 and incorporated herein in its entirety by reference. The forklift tool is attached to a tool trolley (524) that engages and freely rides around the ODV on circular rail (538). A plurality of cams or rollers (540) are disposed on the tool trolley to capture the circular rail with substantially no looseness while allowing the tool trolley to freely slide along the rail. A counter weight trolley (525) is positioned 180 degrees from the forklift tool around circular rail (538). The counterweight trolley also includes a plurality of rollers or cams (540) that engage and slidingly coupled the circular rail (538). The relative spacing between the tool trolley (524) and the counterweight trolley (525) is maintained by one or more linkages (529) coupled therebetween. The linkages do not engage the circular rail. Thus, there are high loading forces concentrated at two poles of the circular rail separated by regions of no loading. That is, the rail forces are unbalanced with high localized loading forces existing at the location of the rail occupied by the tool trolley and counterweight trolley. These high localized forces increase the design requirements of the cams or rollers (540) and increase the friction inherent in the trolley system.
The coupling arrangements shown in FIGS. 1-5 all employ trolleys that freely slide or roll along a circumferential race. The trolleys have a curvature to match the curvature of the race, but they only engage a small portion of the circumferential rail at any time. Thus, loads on the circular rail and coupling mechanisms are concentrated at the trolleys, increasing the design requirements of the trolley components and the friction inherent in the trolley systems.
3. Identification of Features Provided by Some Embodiments of the Invention
A primary object of the invention is to provide an omni-directional service vehicle that is designed and arranged for enhanced maneuverability, which includes a full circumferential revolvable coupling arrangement for improved coupling performance.
Another object of the invention is to provide an omni-directional service vehicle equipped with an appendage for towing, pushing, material handling or similar use revolvably coupled to the ODV by a full circumferential coupling arrangement for lowered friction.
Another object of the invention is to provide an omni-directional service vehicle with a revolvable tool or service appendage having relaxed design requirements.